System for evaluating the condition and performance of a valve and valve operator combination

Abstract

A device for measuring and indicating the forces on a valve stem over at least a portion of the valve strokes is comprised of a strain sensor secured to the valve yoke for sensing strains experienced by the valve yoke. The sensed strains are proportional to the forces on the valve yoke and are equal but opposite to the forces on the valve stem. The strain sensor generates electrical signals proportional to the forces on the valve stem. A display, electrically connected to the strain sensor, is provided for receiving the generated electrical signals and for indicating the forces on the valve stem. A system for evaluating the performance of a valve and valve operator also utilizes the yoke strain sensor in combination with other sensors, including a valve stem motion sensor, a spring pack motion sensor, a motor current sensor and, possibly, a stem strain sensor, as well as an indicator of the condition of torque and limit switches.

I claim: 
     
       1. A device for measuring and indicating the forces on a valve stem of a valve having a valve stem, and a valve yoke over at least a portion of the valve stroke, the device comprising: first strain sensor means for sensing strains experienced by the valve yoke along a strain axis, the first strain sensor means being secured to the valve yoke parallel to the strain axis, the first strain sensor for generating electrical signals proportional to the sensed valve yoke strains, the valve yoke strains being proportional to forces on the valve yoke and being equal and opposite to the forces created on the valve stem during valve operation including seating, backseating and packing forces so that the generated electrical signals are also proportional to the forces on the valve stem; and   display means electrically connected to the first strain sensor means for receiving the electrical signals and for indicating the forces on the valve stem.   
     
     
       2. The device as recited in claim 1 wherein the first strain sensor means is comprised of: a tensile strain member; and   a strain gage bridge circuit connected to the display means, and including at least one strain gage secured to the tensile strain member.   
     
     
       3. The device as recited in claim 2 wherein the first strain sensor means further comprises four strain gages secured to the tensile strain member, two of the strain gages being longitudinally oriented with respect to the member to experience longitudinal strain and two of the strain gages being transversely oriented with respect to the member to experience Poisson strain, the four strain gages forming the strain gage bridge circuit. 
     
     
       4. The device as recited in claim 3 wherein the tensile strain member is a generally flat elongated beam having first and second opposite elongated surfaces, two of the strain gages being secured to the first surface and two of the strain gages being secured to the second surface. 
     
     
       5. The device as recited in claim 4 wherein one longitudinally oriented strain gage and one transversely oriented strain gage is secured to each of said first and second surfaces of the beam. 
     
     
       6. The device as recited in claim 2 wherein the tensile strain member comprises a generally flat elongated beam having mounting means on each end for securing the tensile strain member to the valve yoke, the mounting means being secured to the valve yoke in a predetermined spaced relationship to create a predetermined initial tension in the tensile strain member for facilitating the sensing of both compressive strains in the valve yoke due to tensile forces on the valve stem, and tensile strains in the valve yoke due to compressive forces in the valve stem. 
     
     
       7. The device as recited in claim 2 wherein the display means is comprised of a voltage sensitive meter electrically connected to the strain gage bridge circuit, the voltage sensitive meter having means for indicating the output voltage of the strain gage bridge circuit. 
     
     
       8. The device as recited in claim 7 further comprising means for providing an excitation voltage to the strain gage bridge circuit. 
     
     
       9. The device as recited in claim 1 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples for predetermined time periods to establish a valve stem force digital record; and   means for comparing the valve stem force digital record with a previously stored reference digital record of the forces expected to be experienced by the valve stem during normal operation and for indicating deviations resulting from the comparison.   
     
     
       10. The device as recited in claim 1 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples for predetermined time periods to establish a valve stem force digital record; and   means for comparing the valve stem force digital record with corresponding, previously stored digital records for indicating changes and trends with respect to the forces on the valve stem over time.   
     
     
       11. The device as recited in claim 1 further comprising: second strain sensor means secured to the valve stem for sensing strains experienced by the valve stem and for generating electrical signals proportional thereto;   means for applying a force to the valve stem to create a strain in the valve stem; and   comparison means for receiving the signals generated by the first and second strain sensor means and for comparing changes in the received signals resulting from the application of a force to the valve stem by the force means, the comparison means being employed for calibration of the device.   
     
     
       12. A system for evaluating the condition and performance of a valve and valve operator combination, including a valve, a valve operator containing a motor, gearing a spring pack and torque and limit switches, a valve stem extending between the valve operator and the valve, and a valve yoke surrounding the valve stem, the system comprising: first strain sensor means for sensing strains experienced by the valve yoke along a strain axis, the first strain sensor means being secured to the valve yoke parallel to the strain axis, the first strain sensor for generating electrical signals proportional to the sensed valve yoke strains, the valve yoke strains being proportional to forces on the valve yoke and being equal and opposite to the forces created on the valve stem during valve operation including seating, backseating, and packing forces so that the generated electrical signals are also proportional to the forces on the valve stem;   torque and limit switch indicating means for detecting the state of the torque and limit switches and for generating electrical signals; and   display means electrically connected to the first strain sensor means and to the torque and limit switch indicating means for receiving the generated electrical signals and for indicating the forces on the valve stem and the opening and closing of the torque and limit switches to permit identification of a disruption in normal valve operator to valve stem functioning.   
     
     
       13. The system as recited in claim 12 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples representative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples representative of the opening and closing of the torque and limit switches for predetermined time periods to establish a torque and limit switch digital record;   means for comparing the valve stem force digital record with a previously stored reference digital record of the forces expected to be experienced by the valve stem during normal operation and for indicating deviations resulting from the comparison; and   means for comparing the torque and limit switch digital record with a previously stored reference digital record of the opening and closing expected of the torque and limit switches during normal operation and for indicating deviations resulting from the comparison.   
     
     
       14. The system as recited in claim 12 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples representative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples representative of the opening and closing of the torque and limit switches for predetermined time periods to establish a torque and limit switch motion digital record; and   means for comparing the valve stem force digital record with the torque and limit switch digital record for indicating whether the force of the valve stem and the torque and limit switches are acting together or are acting in opposition to each other to more clearly define valve operation.   
     
     
       15. The system as recited in claim 12 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples representative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples representative of the torque and limit switches for predetermined time periods to establish a torque and limit switch motion digital record;   means for comparing the valve stem force digital record with previously stored valve stem force digital records for indicating changes and trends in the valve stem forces over time; and   means for comparing the torque and limit switch digital record with previously stored torque and limit switch digital records for indicating changes and trends in the opening and closing of the torque and limit switches over time.   
     
     
       16. A system for evaluating the condition and performance of a valve and valve operator combination, including a valve, a valve operator, a valve stem extending between the valve operator and the valve, and a valve yoke surrounding the valve stem, the system comprising: first strain sensor means for sensing strains experienced by the valve yoke along a strain axis, the first strain sensor means being secured to the valve yoke parallel to the strain axis, the first strain sensor for generating electrical signals proportional to the sensed valve yoke strains, the valve yoke strains being proportional to forces on the valve yoke and being equal and opposite to the forces created on the valve stem during valve operation including seating, backseating, and packing forces so that the generated electrical signals are also proportional to the forces on the valve stem;   valve stem motion sensor means for detecting motion and direction of movement of the valve stem and for generating electrical signals proportional to the velocity of valve stem movement, the signals having polarity indicative of the direction of valve stem movement; and   display means electrically connected to the first strain sensor means and to the valve stem motion sensor means for receiving all of the generated electrical signals and for concurrently indicating the forces on the valve stem and the corresponding valve stem velocity to permit identification of a disruption in normal valve operator to valve stem functioning.   
     
     
       17. The system as recited in claim 16 wherein the display means further comprises: means for converting the received electrial signals to digital samples;   means for receiving and storing the digital samples representative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples representative of the velocity and direction of valve stem movement for predetermined time periods to establish a valve stem motion digital record;   means for comparing the valve stem force digital record with a previously stored reference digital record of the forces expected to be experienced by the valve stem during normal operation and for indicating deviations resulting from the comparison; and   means for comparing the valve stem motion digital record with a previously stored reference digital record of the velocity and direction of motion expected of the valve stem during normal operation and for indicating deviations resulting from the comparison.   
     
     
       18. The system as recited in claim 16 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples representative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples representative of the velocity and direction of valve stem movement for predetermned time periods to establish a valve stem motion digital record; and   means for comparing the valve stem force digital record with the valve stem motion digital record for indicating whether the force and motion of the valve stem are acting together or are acting in opposition to each other to more clearly define valve operation.   
     
     
       19. The system as recited in claim 16 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples representative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples representative of the velocity and direction of valve stem movement for predetermined time periods to establish a valve stem motion digital record;   means for comparing the valve stem force digital record with previously stored valve stem force digital records for indicating changes and trends in the valve stem forces over time; and   means for comparing the valve stem motion digital record with previously stored valve stem motion digital records for indicating changes and trends in valve stem motion over time.   
     
     
       20. A system for evaluating the condition and performance of a valve and valve operator combination, including a valve, a valve operator containing a motor, gearing, a spring pack and torque and limit switches, a valve stem extending between the valve operator and the valve, and a valve yoke surrounding the valve stem, the system comprising: first strain sensor means for sensing strains experienced by the valve yoke along a strain axis, the first strain sensor means being secured to the valve yoke parallel to the strain axis, the first strain sensor for generating electrical signals proportional to the sensed valve yoke strains, the valve yoke strains being proportional to forces on the valve yoke and being equal and opposite to the forces created on the valve stem during valve operation including seating, backseating, and packing forces so that the generated electrical signals are also proportional to the forces on the valve stem;   spring motion sensor means for detecting motion and direction of movement of the spring pack and for generating electrical signals proportional to the velocity of spring pack movement, the signals having a polarity indicative of the direction of spring pack movement; and   display means electrically connected to the first strain sensor means and to the spring pack motion sensor means for receiving the generated electrical signals and for indicating the forces on the valve stem and the corresponding spring pack velocity to permit identification of a disruption in normal valve operator to valve stem functioning.   
     
     
       21. The system as recited in claim 20 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples representative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples representative of the velocity and direction of spring pack movement for predetermined time periods to establish a spring pack motion digital record;   means for comparing the valve stem force digital record with a previously stored reference digital record of the forces expected to be experienced by the valve stem during normal operation and for indicating deviations resulting from the comparison; and   means for comparing the spring pack motion digital record with a previously stored reference digital record of the velocity and direction of motion expected of the spring pack during normal operation and for indicating deviations resulting from the comparison.   
     
     
       22. The system as recited in claim 20 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples representative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples representative of the velocity and direction of spring pack movement for predetermined time periods to establish a spring pack motion digital record; and   means for comparing the valve stem force digital record with the spring pack motion digital record for indicating whether the force of the valve stem and the motion of the spring pack are acting together or are acting in opposition to each other to more clearly define valve operation.   
     
     
       23. The system as recited in claim 20 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples representative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples represenative of the velocity and direction of spring pack movement for predetermined time periods to establish a spring pack motion digital record;   means for comparing the valve stem force digital record with previously stored valve stem force digital records for indicating changes and trends in the valve stem forces over time; and   means for comparing the spring pack motion digital record with previously stored spring pack motion digital records for indicating changes and trends in spring pack motion over time.   
     
     
       24. A system for evaluating the condition and performance of a valve and valve operator combination, including a valve, a valve operator containing a motor, gearing, a spring pack and torque and limit switches, a valve stem extending between the valve operator and the valve, and a valve yoke surround the valve stem, the system comprising: first strain sensor means for sensing strains experienced by the valve yoke along a strain axis, the first strain sensor means being secured to the valve yoke parallel to the strain axis, the first strain sensor for generating electrical signals proportional to the sensed valve yoke strains, the valve yoke strains being proportional to the forces on the valve yoke and being equal and opposite to the forces created on the valve stem during valve operation including seating, backseating, and packing forces so that the generated electrical signals are also proportional to the forces on the valve stem;   motor current sensor means for detecting the flow of current through the motor and for generating electrical signals proportional to the motor current and   display means electrically connected to the first strain sensor means and to the motor current sensor means for receiving the generated electrical signals and for indicating the forces on the valve stem and the corresponding motor current to permit identification of a disruption in normal valve operator to valve stem functioning.   
     
     
       25. The system as recited in claim 24 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples representative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples representative of motor current for predetermined time periods to establish a motor current digital record;   means for comparing the valve stem force digital record with a previously stored reference digital record of the forces expected to be experienced by the valve stem during normal operation and for indicating deviations resulting from the comparison; and   means for comparing the motor current digital record with a previously stored reference digital record of the motor current expected during normal operation and for indicating deviations resulting from the comparison.   
     
     
       26. The system as recited in claim 24 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples represenative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples representative of motor current for predetermined time periods to establish a motor current digital record; and   means for comparing the valve stem force digital record with the motor current digital record for indicating whether the force of the valve stem and the motor current are acting together or are acting in opposition to each other to more clearly define valve operation.   
     
     
       27. The system as recited in claim 24 wherein the display means further comprises: means for converting the received electrical signals to digital samples;   means for receiving and storing the digital samples represenative of the forces on the valve stem for predetermined time periods to establish a valve stem force digital record, and for receiving and storing the digital samples represenative of the motor current for predetermined time periods to establish a motor current digital record;   means for comparing the valve stem force digital record with previously stored valve stem force digital records for indicating changes and trends in the valve stem forces over time; and   means for comparing the motor current digital record with previously stored motor current digital records for indicating changes and trends in motor current over time.